Fatigue Design Curves for Industrial Applications: A Review

In the present paper, a review on the design curves for safe–life fatigue design is provided. The methodologies available in the literature for the assessment of the strain–life and stress–life design curves have been analyzed, focusing also on the industrial practice for the design of critical components. The low-cycle fatigue (LCF), high-cycle fatigue (HCF), and very high cycle fatigue (VHCF) life ranges have been considered in the analyses. Design curves should take into account the randomness associated with the material parameter estimation and model it in a probabilistic framework. The analyses carried out in the paper have shown that methodologies based on shifting the median curve or the best-fitting curve by a fixed safety factor or a safety factor dependent on the reliability and confidence targets are among the most used. On the other hand, in several research works, more complex statistical models and methodologies, for example, based on the maximum likelihood principle or the bootstrap approach, have been proposed but are less widespread because they require a more complex implementation. The strengths and the weaknesses of the investigated methodologies have been discussed, providing also indications on future research trends.